These rains and clouds are produced by localized convective lifting In very

These rains and clouds are produced by localized

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heavy rains, but are usually widely scattered. These rains and clouds are produced by localized convective lifting . In very unstable air, the clouds are towering and are usually accompanied by heavy precipitation. This level of instability is usually associated with a lifting mechanism other than localized convective lifting .
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Conditional Instability This is the most common type of atmospheric instability. Occurs when moist air has an environmental lapse rate between the dry and wet adiabatic rates. (The environmental lapse rate in this case would be between 6 0 C and 10 0 C per 1000 meters.) Conditional instability means the air is stable with respect to an unsaturated parcel of air , and unstable with respect to a saturated parcel of air . The rising parcel of air is cooler than the surrounding air for the first perhaps 2000, 3000, or 4000 meters. But the release of latent heat above the lifting condensation level means the parcel becomes warmer than the surrounding air. From this point the parcel will rise without an outside force .
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Conditional instability depends upon whether or not the rising air is saturated . The term “conditional” is used, because the air must be forced upwards by lifting mechanisms like mountains before it reaches the level where it is unstable and rises on its own .
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Summary 1) Warming the air at Earth’s surface generally increases instability , as the environmental lapse rate increases . 2) Cooling the air at Earth’s surface generally increases the stability , as the environmental lapse rate decreases . During the daytime the air tends to be more unstable, because of surface heating by the Sun. After the Sun goes down, surface cooling renders the air stable.
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  • Fall '16
  • Mark Smith
  • Heat, Atmospheric thermodynamics, Instability, 100m, 1000 feet

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